This is an inter-departmental venture of Pediatrics, Medicine, and Biomedical Engineering, and the Applied Physics Laboratory of Johns Hopkins. There are five individual projects: (a) Dynamics of arterial vascular aging: concerned with arterial wave transmission--in particular, distortion of the pressure wave as it travels distally, and pulsewave velocity. (b) Pulsatile studies as related to plaque formation: to determine those characteristics of flow and arterial properties that account for the localization of plaques. (c) Improved methods of non-invasive recording of intra-arterial pulses: measurements of pulsewave velocity; possible external markers for onset of aortic pressure in apexcardiogram, photoplethysmogram, and electrocardiogram. Pulsewave velocity will be compared with intravascular measurements. Detailed measurements of the quantitative force of the pulse at the radial artery will be made. (d) Application of sonic reflectometry to detection of early arteriosclerosis: to be able to detect a plaque .2 mm thick by 10 mm in diameter, the maximum considered to represent 'early' arterial plaques. Commercially available equipment will have to be modified in order to be able to detect changes in plaques. (e) Compliance with dietary intervention therapy in children with hyperlipoproteinemia: a study exploring the relevant parameters of the health belief model. Others will be interviewed relative to those psychosocial dimensions thought to be related to compliance. Type II families will be randomized, one receiving dietary instruction only, and the other both instruction and special foods.